Capacitors are electrical components that store electrical energy in an electromagnetic field between electrodes that are separated by a dielectric insulator. Each electrode carries a charge that is opposite in polarity to the charge on the other electrode. Capacitors find many applications in a wide variety of electric circuits. For example, implantable defibrillators and pacemakers provide cardiac rhythm management therapy to the heart in the form of low energy pacing pulses to evoke heart contractions and high energy electrical countershocks to interrupt certain arrhythmias. Such cardiac rhythm management devices include circuits that sense heart activity and control the delivery of therapy. Many of these circuits use capacitors. For example, capacitors are used to store energy for the delivery of low or high energy therapy to the heart. Capacitors are also used to in filter circuits that remove unwanted signals. In another example, capacitors are used to store energy for stabilizing power supply circuits.
One goal in designing electronic devices is to reduce the size of the electronic device, which makes the device more portable. In implantable devices, size reduction is not just important, it is critical. A smaller device is easier for the physician to implant in the patient. Moreover, by reducing the size of other components in an implantable device, a larger battery can be used, prolonging the implanted longevity of the device before a replacement device is required. Increasing the implanted longevity of such devices reduces the cost of the patient's medical treatment, which is extremely important in the present environment of rising medical costs.
Many discrete capacitors used in implantable medical devices are surface mount devices that are mounted onto multilayer hybrid substrate circuit boards. Unfortunately, such capacitors often consume a large area of the circuit board. This tends to increase the size of the implantable device, or alternatively, tends to reduce implantable longevity by reducing the battery size that can be accommodated in a particular size device. Thus, there is a critical need to more effectively use discrete capacitors in implantable medical devices and other electronic circuits.